Low Concentrations Of Sodium Dodecyl Sulfate Research Articles

Control of the Colloidal and Adsorption Behaviors of Chitin Nanocrystals and an Oppositely Charged Surfactant at Solid, Liquid, and Gas Interfaces.

Chitin has a unique hierarchical structure, spanning the macro- and nanoscales, and presents chemical characteristics that make it a suitable component of multiphase systems. Herein, we elucidate the colloidal interactions between partially deacetylated chitin nanocrystals (cationic ChNC) and an anionic surfactant, sodium dodecyl sulfate (SDS). We investigate charge neutralization and association (electrophoretic mobility, surface tensiometry, and quartz crystal microgravimetry) and their role in the stabilization of Pickering emulsions. We find SDS adsorption and association with ChNC under distinctive regimes: At low SDS concentration, submonolayer assemblies form on ChNC, driven by the hydrophobic effect and electrostatic interactions. With the increased SDS concentration, bilayers or patchy bilayers form, followed by adsorbed hemimicelles and micelles. We further suggested the role of hydrophobic effects in the observed colloidal transitions and complex conformations. At the highest SDS concentration tested, charge neutralization and SDS/ChNC flocculation take place. Remarkably, at given concentrations, adsorbed SDS endows the chitin nanoparticles with an effective hydrophobicity that opens the opportunity to achieve tailorable Pickering stabilization. Hence, a facile route is proposed by in situ modification by SDS physisorption, which extends the potential of renewable nanoparticles in the formulation of complex fluids, for instance, those relevant to household and healthcare products.

The investigation of the binding ability between sodium dodecyl sulfate and Cu (II) in urban stormwater runoff

The simultaneous presence of heavy metals and surfactants in runoff induces complexation and ecological harm during migration. However, interactions between these pollutants are often overlooked in past studies. Thus, investigating heavy metal-surfactant complexes in runoff is imperative. In this work, Cu (II) and sodium dodecyl sulfate (SDS) were selected to investigate the interaction between heavy metals and surfactants due to the higher detected frequency in runoff. Through 1H NMR and FTIR observation of hydrogen atom nuclear displacement and functional group displacement of SDS, the change of SDS and Cu (II) complexation was obtained, and then the complexation form of Cu (II) and SDS was verified. The results showed that solution pH values and ionic strength had significant effects on the complexation of Cu (II). When the pH values increase from 3.0 to 6.0, the complexation efficiency of SDS with Cu (II) increased by 12.12% at low concentration of SDS, which may be attributed to the excessive protonation in the aqueous solution at acidic condition. The increase of ionic strength would inhibit the complexation reaction efficiency by 19.57% and finally reached the platform with concentration of NaNO3 was 0.10 mmol/L, which was mainly due to the competitive relationship between Na (I) and Cu (II). As a general filtering material in stormwater treatment measures, natural zeolite could affect the interaction between SDS and Cu (II) greatly. After the addition of SDS, the content of free Cu (II) in the zeolite-SDS-Cu (II) three-phase mixed system was significantly reduced, indicating that SDS had a positive effect on the removal of Cu (II) from runoff. This study is of great significance for investigating the migration and transformation mechanism of SDS and Cu (II) in the future and studying the control technology of storm runoff pollution.

Cork granules for remediation of soils contaminated with lindane

This work aims to assess the effectiveness of an integrated approach combining surfactant-assisted soil washing (SASW) and cork granules for removing lindane from contaminated soil. It focuses on the evaluation of cork granules (raw and regranulated) as natural sorbents for lindane and on the feasibility of the combination of this physical treatment with surfactant-enhanced soil washing to face the remediation of soil polluted with this hazardous pesticide. The results demonstrate that cork can efficiently retain lindane contained in aqueous solutions and dispersions consisting of mixtures of lindane and sodium dodecylsulfate (SDS) surfactant. Performance improves when using regranulated cork because of its higher affinity for nonpolar species. For lower concentrations of lindane and without surfactant, the raw cork granules presented a sorption capacity of 3.02 mg g− 1, while the regranulated cork presented 6.52 mg g−1. When using a much higher concentration of lindane and SDS, the capacities were 1.90 and 8.21 mg g−1 for raw and regranulated cork, respectively. As well, soil washing with SDS can separate efficiently lindane from spiked soil. It was also observed that the integration of both treatments was feasible, but not as efficient as initially expected. It exhibited a non-expected antagonistic effect caused by the entrapping of the lindane into SDS micelles, which makes it not readily available for sorption. Hence, the higher the amount of SDS the lower the lindane retained by the cork. If the aim is to eliminate lindane with cork specifically, the use of low concentrations of SDS in the combined treatment is encouraged, resulting in an uptake capacity for lindane of 80% from the soil. However, better overall results are achieved when higher concentrations of SDS are used where about 91% of lindane was removed from the soil remaining mainly in the liquid phase. Dichlorination caused by interaction with hydroxyl ions is also observed, being less important in the case of using cork because it attains operation at mild conditions. The results demonstrate that the integration of processes in soil remediation does not always yield expected outcomes and they enhance the knowledge about environmental technologies and their interactions.

(Invited) Kinetics of SWCNT Coating Displacement By ssDNA Depends on SWCNT Structure

Non-covalent hybrids formed by suspending single-wall carbon nanotubes (SWCNTs) in single-stranded DNA (ssDNA) present novel phenomena and suggest potential applications in biomedicine and nanotube sorting. Although the structures of these hybrids have been simulated using molecular dynamics calculations, much more experimental research is needed to understand their properties. In this study, selective interactions between SWCNTs and ssDNA are probed by measuring the kinetics by which ssDNA displaces SDS (sodium dodecyl sulfate) coatings on the nanotube surfaces. We used samples initially suspended in a low concentration of SDS to allow the coating displacement to occur and to suppress formation of free SDS micelles. The displacement process was monitored by time-dependent measurements of SWCNT fluorescence intensities and wavelengths. Our experiments showed very smooth decreases in fluorescence intensity and red-shifts in fluorescence wavelengths during the displacement process. Through a series of measurements, we found that ssDNA sequences with repeated guanine (G) and thymine (T) bases showed systematic patterns in the coating displacement kinetics. One result is that SDS displacement depends strongly on oligo length, with (GT)3 showing an initial rate constant 500 times greater than that of (GT)20. For shorter oligos in the (GT) n series, we observe an inverse dependence of initial rate constant on SWCNT diameter, with SDS displacement from (6,5) more than twice as fast as from (8,7). However, this diameter dependence is not present for (GT) n oligos with n greater than 6. We also find a distinct and systematic dependence of initial rate constant on nanotube chiral angle for (GT)5 and (GT)6. This effect gives a factor of ~3 difference between (9,1) and (6,5) despite their identical diameters. We empirically find these initial rate constants to vary as (SWCNT diameter)-4(cos 3θ)-y with y = -1/2 for (GT)5 and -1 for (GT)6. In addition, the full displacement kinetic traces are well fitted by double exponential kinetics, with rate constants and amplitudes dependent on SWCNT diameter. A two-step kinetic model for the displacement process will be presented to account for these findings.

Effect of Drinking Water Salt Content on the Interaction between Surfactants and Bacteria.

Sodium dodecyl sulfate (SDS) is a common surfactant used in various hygienic products. Its interactions with bacteria were studied previously, but the three-way interaction between surfactants, bacteria, and dissolved salts in the context of bacterial adhesion has not been studied. Here, we examined the combined effects of SDS (at concentrations typical of everyday hygienic activities) and salts, sodium chloride, and calcium chloride (at concentrations typically found in tap water) on the adhesion behavior of the common opportunistic pathogen Pseudomonas aeruginosa. We found that bacterial adhesion in the absence of SDS was dependent on the cation concentration rather than the total ionic strength and that combined treatment with several millimolar NaCl and SDS can increase bacterial adhesion. The addition of low concentrations of SDS (2 mM) to tens to hundreds millimolar concentrations of NaCl, typical of systems that suffer seawater incursion, reduced bacterial adhesion dramatically. Combined treatment with Ca+2 (in concentrations typical of those found in hard water) and SDS produced a small increase in total adhesion but a dramatic increase in the strength of adhesion. We conclude that the type and concentration of salts in water can have a considerable effect on the efficacy of soap in reducing bacterial adhesion and should be taken under consideration in critical applications. IMPORTANCE Surface-adhering bacteria are a reoccurring problem in many settings, including households, municipal water systems, food production facilities, and hospitals. Surfactants, and specifically sodium dodecyl sulfate (also known as SDS/SLS), are commonly used to remove bacterial contamination, but data regarding the interaction of SDS with bacteria and especially the effects of water-dissolved salts on this interaction are lacking. Here, we show that calcium and sodium ions can dramatically affect the efficacy of SDS on bacterial adhesion behavior and conclude that salt concentrations and ion species in the water supply should be considered in SDS applications.

Morphological Effects of Au Nanoparticles on Electrochemical Sensing Platforms for Nitrite Detection

Au nanoparticles were synthesized in a soft template of pseudo-polyanions composed of polyvinylpyrrolidone (PVP) and sodium dodecyl sulfate (SDS) by the in situ reduction of chloroauric acid (HAuCl4) with PVP. The particle sizes and morphologies of the Au nanoparticles were regulated with concentrations of PVP or SDS at room temperature. Distinguished from the Au nanoparticles with various shapes, Au nanoflowers (AuNFs) with rich protrusion on the surface were obtained at the low final concentration of SDS and PVP. The typical AuNF synthesized in the PVP (50 g·L−1)–SDS (5 mmol·L−1)–HAuCl4 (0.25 mmol·L−1) solution exhibited a face-centered cubic structure dominated by a {111} crystal plane with an average equivalent particle size of 197 nm and an average protrusion height of 19 nm. Au nanoparticles with four different shapes, nanodendritic, nanoflower, 2D nanoflower, and nanoplate, were synthesized and used to modify the bare glassy carbon electrode (GCE) to obtain Au/GCEs, which were assigned as AuND/GCE, AuNF/GCE, 2D-AuNF/GCE, and AuNP/GCE, respectively. Electrochemical sensing platforms for nitrite detection were constructed by these Au/GCEs, which presented different detection sensitivity for nitrites. The results of cyclic voltammetry (CV) demonstrated that the AuNF/GCE exhibited the best detection sensitivity for nitrites, and the surface area of the AuNF/GCE was 1.838 times of the bare GCE, providing a linear c(NO2−) detection range of 0.01–5.00 µmol·L−1 with a limit of detection of 0.01 µmol·L−1. In addition, the AuNF/GCE exhibited good reproducibility, stability, and high anti-interference, providing potential for application in electrochemical sensing platforms.

Effect of polymer/surfactant complexation on diffusiophoresis of colloids in surfactant concentration gradients

HypothesisA concentration gradient of surfactants in the presence of polymers that non-covalently associate with surfactants will exhibit a continually varying distribution of complexes with different composition, charge, and size. Since diffusiophoresis of colloids suspended in a solute concentration gradient depends on the relaxation of the gradient and on the interactions between solutes and particles, polymer/surfactant complexation will alter the rate of diffusiophoresis driven by surfactant gradients relative to that observed in the same concentration gradient in the absence of polymers. ExperimentsA microfluidic device was used to measure diffusiophoresis of colloids suspended in solutions containing a gradient of sodium dodecylsulfate (SDS) in the presence or absence of a uniform concentration of Pluronic P123 poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) nonionic triblock copolymers. To interpret the effect of P123 on the rate of colloid diffusiophoresis, electrophoretic mobility and dynamic light scattering measurements of the colloid/solute systems were performed, and a numerical model was constructed to account for the effects of complexation on diffusiophoresis. FindingsPolymer/surfactant complexation in solute gradients significantly enhanced diffusiophoretic transport of colloids. Large P123/SDS complexes formed at low SDS concentrations yielded low collective solute diffusion coefficients that prolonged the existence of strong concentration gradients relative to those without P123 to drive diffusiophoresis.

Rapid formation of methane hydrate in environment-friendly leucine-based complex systems

Given the growing demand for natural gas (NG) in energy supply systems worldwide, solidified natural gas (SNG) is viewed as a potential NG storage and transportation method owing to its numerous advantages. However, using significant amounts of sodium dodecyl sulfate (SDS) to improve its slow formation kinetics has a negative influence on the environment, and severe foaming hinders the system's recovery. To overcome the associated issues, the main promoter has been chosen to be the ecologically safe and non-foaming L-leucine, with low concentrations of SDS and NaCl, as well as glass beads of various particle sizes, added to achieve synergistic effects. The hydrophobic micro-regions created by the leucine molecules, as well as the porous hydrate characteristics, considerably enhanced hydrate formation in the leucine-based complex system. At the effective promotion concentration, the SDS dosage is reduced by 60–90%. Owing to their strong promotion effect and non-foaming feature, yielding almost non-toxic properties, the LS1 and LN4 systems may be employed commercially. With a target of advancing SNG technology, this study serves as a reference for future developments of SNG technology based on the idea of environmental friendliness.

EFFECTS OF SYNTHESIS CONDITIONS ON STRUCTURE OF TIN NANORODS PREPARED BY SURFACTANT-ASSISTED CHEMICAL REDUCTION METHOD

Metallic nanorods/nanowires have recently become the focus of intensive research due to their unique properties and have been used to fabricate electronic, energy devices and sensors in nanoscale. In this study, tin nanorods were synthesized through a surfactant assisted chemical reduction method in aqueous solutions at low temperature (~ 0 oC). Sodium dodecyl sulfate (SDS) and sodium borohydride (NaBH4) were used as the surfactant and reductant, respectively. Parameters such as pH, surfactant concentration, and temperature were studied to control the diameter and length of the nanorods formed. The structure, composition and surface morphology of the obtained products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that the morphology as well as the aspect ratio of tin nanorods could be effectively controlled by adjusting the parameters of the synthesis process. It was found that tin nanoparticles were formed at 30 oC while nanorods appeared at lower temperatures (0, 5 oC). A low SDS concentration of 4 mM helped to form Sn nanoparticles but higher SDS concentrations of 8, 12 mM facilitated the growth of nanorods. The increase of SDS concentration reduced the length of nanorods. pH values less than 4.5 were found to be favorable to the formation of nanorods.

On the association between poly(vinyl alcohol) and sodium dodecyl sulfate and its effect on liquid–liquid interfacial tension: A mathematical model

AbstractAssociation between poly(vinyl alcohol‐co‐vinyl acetate) copolymer (PVA) and sodium dodecyl sulfate (SDS) was studied experimentally and theoretically. It was found that, for the ethyl acetate‐aqueous phase interface in which PVA was previously adsorbed, the interfacial tension (γ) increases abruptly to a maximum and then exhibits a relatively mild decay with the addition of SDS to the aqueous phase. The theoretical results indicate that vinyl acetate (VAc) segments determine γ. However, for relatively low concentrations of SDS (CSDS), this latter plays a major role because through its association with the VAc segments it modulates the extent to which PVA is adsorbed at the interface, indirectly determining the value of γ. As CSDS approaches to the CMC value for SDS, its influence on γ decreases because SDS tends to self‐assembly rather than associates with VAc. These model predictions are consistent with experimental findings reported in the literature.

Impact of a Hydrocarbon Surfactant on the Retention and Transport of Perfluorooctanoic Acid in Saturated and Unsaturated Porous Media.

The transport and retention behavior of perfluorooctanoic acid (PFOA) in the presence of a hydrocarbon surfactant under saturated and unsaturated conditions was investigated. Miscible-displacement transport experiments were conducted at different PFOA and sodium dodecyl sulfate (SDS) input ratios to determine the impact of SDS on PFOA adsorption at solid-water and air-water interfaces. A numerical flow and transport model was employed to simulate the experiments. The PFOA breakthrough curves for unsaturated conditions exhibited greater retardation compared to those for saturated conditions in all cases, owing to air-water interfacial adsorption. The retardation factor for PFOA with a low concentration of SDS (PFOA-SDS ratio of 10:1) was similar to that for PFOA without SDS under unsaturated conditions. Conversely, retardation was greater in the presence of higher levels of SDS (1:1 and 1:10) with retardation factors increasing from 2.4 to 2.9 and 3.6 under unsaturated conditions due to enhanced adsorption at the solid-water and air-water interfaces. The low concentration of SDS had no measurable impact on PFOA air-water interfacial adsorption coefficients (Kia) determined from the transport experiments. The presence of SDS at the higher PFOA-SDS concentration ratios increased the surface activity of PFOA, with transport-determined Kia values increased by 27 and 139%, respectively. The model provided very good independently predicted simulations of the measured breakthrough curves and showed that PFOA and SDS experienced various degrees of differential transport during the experiments. These results have implications for the characterization and modeling of poly-fluoroalkyl substances (PFAS) migration potential at sites wherein PFAS and hydrocarbon surfactants co-occur.

Experimental Study of the Processes of Formation, Drift and Coalescence of Vapor-Gas Bubbles in Aqueous Solutions of Salts and Surfactants in a Sonochemical Reactor

An experimental study of the activity of cavitation processes and the intensity of coalescence of vapor-gas bubbles arising in the volume of a liquid in the presence of ultrasonic (US) exposure in a NaCl salt solution and at various concentrations of sodium dodecyl sulfate (SDS) as a surfactant has been carried out. The process of bubble formation and drift was recorded using a highspeed camera in the plane of the cuvette illuminated by a laser knife. It is shown that the addition of a surfactant to an aqueous solution of NaCl salt leads to a partial inhibition of the coalescence of the observed bubbles and a change in the degassing mode of the liquid in the presence of ultrasonic treatment. The maximum activity of cavitation processes and the formation of vapor-gas bubbles was observed in the presence of salt and a low concentration of SDS. Thus, the presence of a surfactant in an aqueous solution of 0.1 M NaCl salt leads to a change in the growth dynamics of the bubble ensemble, since small bubbles are not able to float to the surface, due to the prevalence of viscous and vibrational forces over buoyancy force.

Bed expansion and gas holdup characteristics of bubble–assisted fluidization of liquid–particle suspensions in a HydroFloat cell

The HydroFloat cells made by Eriez are designed for floating coarse particles using fluidization involving bubble–liquid–particle suspensions. The operational optimization and control of these cells can be a challenging task and require various correlations that are difficult to establish by theory. Here, experiments were performed to study the effect of SDS (sodium dodecyl sulfate) on the liquid–particle and bubble–liquid–particle fluidization processes in a laboratory-scale HydroFloat cell. Air was supplied to a perforated circular tube at the bottom to generate the bubbles while irregular coarse quartz particles were fed to the top by a vibrating plate as the solid phase. In the liquid–particle fluidization, the bed expansion (BE) increased with increasing superficial liquid velocity and agreed with the modified Richardson-Zaki equation (within 4% relative error). BE decreased to 12.5% in the presence of SDS at low concentrations. In the bubble–liquid–particle fluidization, BE was reduced by 8.46 – 2.89% and 15.1% with increasing superficial gas velocity and decreasing superficial liquid velocity in the absence of SDS, respectively. In the presence of SDS, BE increased with increasing superficial gas and liquid velocities. High SDS concentrations generated expanded beds with higher heights. Low SDS concentration (0.2 mM) increased the gas holdups by an average of 20% with increasing superficial gas velocity from 1.1 to 3.4 mm/s. Both BE and gas holdup were compared with the available empirical correlations. The estimated BE showed smaller mean absolute relative errors (MAREs) in the absence of SDS than the presence of SDS, while gas holdups yielded large MAREs. The particle sphericity and bubble Reynolds number were incorporated into the Begovich-Watson and Ramesh-Murugesan equations to estimate the BE and gas holdup, respectively. The modified equations significantly improved the predictions. The empirical correlations developed and investigated here would be useful for the operational optimization of the fluidized bed HydroFloat cells.

A surfactant SDS modified carbon paste electrode as an enhanced and effective electrochemical sensor for the determination of doxorubicin and dacarbazine its applications: A voltammetric study

An electrochemical method has been described for the voltammetric oxidation and determination of anticancer drug doxorubicin (DOX) and dacarbzine (DTIC) were investigated by cyclic voltammetry (CV) and differential pulse voltammetric (DPV) techniques using in the presence of an enhancing agent sodium dodecyl sulfate (SDS) immobilizing at the carbon paste electrode. The solution conditions and operating parameters were optimized. We studied electrochemical parameters of DOX and DTIC like the effect of scan rate (diffusion controlled), heterogeneous rate constant, pH and from the concentration effect both drugs gives lower detection limit at SDS modified carbon paste electrode (SDS/MCPE). An analytical method was developed for the determination of DOX and DTIC in phosphate buffer solution (PBS) at pH 6.2 as a supporting electrolyte by CV and DPV techniques. A plausible electrochemical oxidation mechanism of DOX and DTIC was proposed. The results indicated that the voltammetric response of DOX and DTIC drugs were improved distinctly in the low concentration of SDS, suggesting that SDS exhibiting a noticeable enhancement effect to the electrocatalytic activity of DOX and DTIC drugs. The SDS/MCPE gives well separated four enhancement peaks for dopamine, serotonin, DOX and DTIC by CV and DPV system. The DOX and DTIC with excipients and interaction of DOX with DNA-time curve were also obtained by the established method. The developed sensor could be a successful monitor for clinical analysis, quality control and other therapeutic drugs.

Response of life-history traits of estuarine nematodes to the surfactant sodium dodecyl sulfate

Species responses to stress are expected to be dependent on their life-history strategy. In this study, we compare the responses of two free-living marine nematodes, Litoditis marina and Diplolaimella dievengatensis, both considered opportunistic, fast-growing, and stress-tolerant species, to the exposure to sublethal concentrations of sodium dodecyl sulfate (SDS) surfactant. Specifically, we evaluated the growth and reproduction rates, as well as the survival of individuals exposed from eggs and/or juveniles (J1) onwards. Exposure to SDS significantly affected the growth and reproduction rates of both species. However, whereas growth and reproduction rates of D. dievengatensis were significantly enhanced at low and intermediate concentrations of SDS (0.001% and 0.003%), for L. marina both parameters were significantly reduced by all SDS concentrations tested (0.001%, 0.003% and 0.006%). Exposure to SDS did not affect the survival of adult nematodes of D. dievengatensis, while for L. marina, survival of males exposed to 0.006% SDS was significantly reduced compared to the control. Responses of the life-history traits growth, fecundity and survival did not exhibit clear trade-offs. The contrasting responses of D. dievengatensis and L. marina indicate that biologically and ecologically similar species can have remarkably distinct tolerances to stress, and that, in agreement with recent studies, rhabditid nematodes cannot a priori be considered very stress tolerant. Consequently, single species traits and phylogenetic relatedness are poor predictors of nematode responses to toxic stress posed by anthropogenic activities.

Novel cytokine marker available for skin irritation testing of medical devices using reconstructed human epidermis models

In biological safety evaluation of medical devices, false-negative results have been observed during skin irritation testing using the reconstructed human epidermis (RhE) model when measuring cell viability as a single marker. Therefore, to improve testing accuracy, this study conducted a comprehensive survey and performance evaluation of cytokines to identify a second marker. In addition to IL-1α, macrophage migration inhibitory factor (MIF) was newly identified as a candidate marker, in the Bio-Plex assay of EpiDerm model exposed to polymer sample extracts. Irritation based on cell viability level was not accurately determined in LabCyte model using silicone spiked with 25% heptanoic acid (HA). By contrast, the irritation potency was accurately assessed in detail by measuring IL-1α or MIF. Further, IL-1α and MIF levels in EpiDerm, LabCyte, and EpiSkin models stimulated with sodium dodecyl sulfate (SDS) were inversely correlated with cell viability, and were detected even at low SDS concentrations without cell toxicity. Additionally, MIF demonstrated greater S/N ratio and dose-dependency at high SDS concentrations in some models compared to IL-1α. These results indicated that MIF might be a useful second marker for improving the sensitivity and accuracy of skin irritation testing with RhE models.

Sodium dodecyl sulfate improves the treatment of waste paper with rumen fluid at lower concentration but decreases at higher condition

Rumen fluid has been applied to lignocellulosic biomass digest for methane production, and various feed supplements have been shown to improve ruminant digestion of lignocellulosic biomass. Therefore, we investigated the effects of sodium dodecyl sulfate (SDS) on the pretreatment of lignocellulosic biomass with rumen fluid and subsequent methane fermentation. SDS was mixed with rumen fluid at concentrations of 0.1, 0.2, 0.4, and 0.8 g/L. After SDS addition, the waste paper was pretreated with rumen fluid at 37 °C for 6 h. SDS addition decreased the number of surviving rumen ciliates after pretreatment. SDS addition increased the dissolved chemical oxygen demand during pretreatment; however, SDS addition did not increase the volatile fatty acid concentration. After pretreatment, batch methane fermentation of pretreated waste paper was performed at 35 °C for 45 days. SDS addition at 0.1 and 0.2 g/L shortened the waste paper digestion time and enhanced methane gas production compared to the control. By contrast, SDS addition at 0.4 and 0.8 g/L remarkably inhibited methane production from waste paper. These findings suggest that low concentrations of SDS can improve the efficiency of lignocellulosic biomass pretreatment with rumen fluid, and can enhance methane production from waste paper.

Electrophoretic NMR Characterization of Charged Side Chain Cationic Polyelectrolytes and Their Interaction with the Anionic Surfactant, Sodium Dodecyl Sulfate.

Oppositely charged polymers and surfactants show a complex phase behavior with large regions of solubility and insolubility dependent on the concentrations of the species present. Here, a series of quaternized hydroxyethyl cellulose (cationic) polymers have been characterized by pulsed-gradient spin-echo NMR (PGSE-NMR) and electrophoretic NMR (eNMR) in simple aqueous (D2O) solutions and in combination with the oppositely charged (anionic) surfactant, sodium dodecyl sulfate (SDS). Analysis of the effective charge on the polymer derived from both the eNMR and PGSE-NMR results yields a readily interpretable insight into the polymer behavior; the effective charge on the polymer at infinite dilution shows a linear relationship with the degree of modification. On addition of low concentrations of SDS, typically Csurf < 5 mM, the surfactant interacts with the charged polymers, leading to substantial changes in the dynamics of the system (polymer diffusion, viscosity). At these levels of surfactant addition, there is no macroscopic phase separation. Further, with the absence of an interaction with the parent, the uncharged polymer strongly suggests that the SDS only interacts with the charged moieties present on the functionalized side groups and not the polymer backbone. Ultimately, the charge on the soluble polymer/surfactant complex was found to depend linearly on the level of surfactant binding across a series of polymers with differing levels of modification with the charge becoming effectively zero at the macroscopic phase separation boundary.

Introduction of a nonionic sugar-based surfactant to an oppositely charged hydrophobically modified polyelectrolyte and surfactant binary system

Interactions between polymer and surfactant provide the system a variety of properties that can be readily used by industries to achieve desired features for their products and formulations. Inclusion of a third component to the binary system is expected to present synergistic or antagonistic effects, and also lead to preferred advantages, such as reduced quantities of the components to present a comparable performance and improved environmental-benignity. In this study a sugar-based surfactant n-Dodecyl β-D-Maltoside (DM) is introduced into an oppositely charged hydrophobically modified polyelectrolyte-surfactant system comprised by a guar grafted with hydroxypropyl trimethyl ammonium chloride (Guar-HTAC) and Sodium Dodecylsulfate (SDS). By following the pattern curves of surface tension, polarity and turbidity profiles, it was found that DM plays a crucial role in the interaction process: DM leads to the formation of a soluble but surface active complex which has not been observed in the Guar-HTAC/SDS and SDS/DM systems; since DM cooperates with SDS to form micelles at much lower SDS concentrations, under certain conditions it is SDS/DM micelles instead of single SDS or DM molecules that interact with Guar-HTAC. Such behaviors are believed to be resulted from the structures of the complexes formed by the three components. Molecular structures of these formed complexes need to be investigated following this study.

Unraveling the molecular mechanism of the effects of sodium dodecyl sulfate, salts, and sugars on amyloid fibril formation in camel IgG.

Sodium dodecyl sulfate (SDS) is an anionic surfactant that can be used to stimulate protein fibrillation in vitro. Here, we investigated the effects of SDS on camel IgG aggregation at pH 3.5 and 7.4. SDS-induced amyloid fibril formation in camel IgG was examined by turbidity measurements, Rayleigh scattering, Thioflavin T (ThT) fluorescence, intrinsic fluorescence, circular dichroism (CD), and transmission electron microscopy (TEM). The results suggest that low SDS concentrations (0.2-2.0 mM) induce amyloid-like aggregates of camel IgG at pH 3.5, indicating an SDS/camel IgG ratio below 1000. However, in the presence of higher concentrations of SDS (2.5-10.0 mM), amyloid fibril formation was not observed. Furthermore, at the higher concentrations, the β-sheet structure of camel IgG was transformed into a α-helical structure. The amyloid fibril formation was not observed in the presence of SDS at pH 7.4. Additionally, the role of salts and sugars was evaluated in the SDS-induced aggregation process. Interestingly, in the presence of 0.15 N of NaCl and (NH4)2SO4, SDS promoted camel IgG aggregation up to very high concentrations of SDS (0.2-10.0 mM; SDS/camel IgG ratio, 95-4750) and no suppression was observed. Moreover, osmoprotectants (trehalose and sucrose) were ineffective, neither promoting nor inhibiting the SDS-induced aggregation process. However, at pH 3.5, electrostatic and hydrophobic interactions, and hydrogen bonds were the major contributing factors in SDS-induced fibrillation. However, no aggregation was observed at pH 7.4 due to electrostatic repulsion between SDS and camel IgG because both of these molecules have overall similar charges.